Nucleoside aryl phosphoramidates and their use as anti-viral agents for the treatment of hepatitis C virus

ABSTRACT

Compounds having the general formula (I): 
                         
are provided which have enhanced inhibitory potency and are thus useful in methods of prophylaxis or treatment of a viral infection such as hepatitis C virus. The compounds are phosphoramidate derivatives of nucleoside compounds derived from bases such as adenine and guanine. The glycoside moiety of the nucleoside compound can be substituted at the ss-2′ position with methyl and the phosphoramidate group can be 1-naphthyl linked by —O— to the P atom. These compounds can be administered as pharmaceutical compositions, and methods for their preparation are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 371 application based on PCT/GB2007/004480,filed Nov. 23, 2007.

The present invention relates to chemical compounds, their preparationand their use in the treatment and prophylaxis of viral infections,particularly in homo sapiens. Particularly, although not exclusively,the present invention relates to chemical compounds useful as anti-viralagents active with respect to hepatitis C virus (HCV).

WO 2006/012078 A describes certain nucleoside aryl phosphoramidates,their synthesis, and their use as precursors to inhibitors ofRNA-dependent RNA viral polymerase, particularly their use as precursorsto inhibitors of hepatitis C virus (HCV) NS5B polymerase, as precursorsto inhibitors of HCV replication, and for the treatment of hepatitis Cinfection.

WO 2006/100439 A relates to phosphoramidates of cladribine,isocladribine, fludaribine and clofarbine and their use in the treatmentof a cancer such as leukaemia.

The intracellular kinase-mediated activation of the compounds describedin WO 2006/100439 A with respect to their treatment of cancer isdifferent to the intracellular kinase-mediated activation required inthe treatment and prophylaxis of viral infections.

It is an object of the present invention to provide novel chemicalcompounds that provide improved prophylaxis and treatment of viralinfections in homo sapiens, in particular improved prophylaxis andtreatment of hepatitis C infection in homo sapiens.

According to a first aspect of the present invention there is provided acompound of formula I:

wherein:

Ar comprises two or more fused aromatic rings and is selected from thegroup consisting of C₉₋₃₀aryl and C₆₋₃₀heteroaryl, any of which ringsare optionally substituted;

T is selected from the group consisting of hydrogen (—H), fluoro (—F),azido (—N₃), amino (—NH₂), hydroxy (—OH), C₁₋₃alkyl (C₁₋₃—), C₁₋₃alkoxy(C₁₋₃O—), mercapto (—SH) and C₁₋₃alkylthio (C₁₋₃S—);

V is selected from the group consisting of —OT′, hydrogen (—H), fluoro(—F) and chloro (—Cl), where T′ is selected from the group consisting ofhydrogen (—H), methyl (—CH₃), C₁₋₁₆alkylcarbonyl (C₁₋₁₆alkyl-C(═O)—),C₂₋₁₈alkenylcarbonyl (C₂₋₁₈alkenyl-C(═O)—), C₁₋₁₀alkoxycarbonyl(C₁₋₁₀alkyl-O—C(═O)—), C₃₋₆cycloalkylcarbonyl (C₃₋₆cycloalkyl-C(═O)—)and C₃₋₆cycloalkyloxycarbonyl (C₃₋₆cycloalkyl-O—C(═O)—);

T″ is selected from the group consisting of hydrogen (—H), methyl(—CH₃), C₁₋₁₆alkylcarbonyl (C₁₋₁₆alkyl-C(═O)—), C₂₋₁₈alkenylcarbonyl(C₂₋₁₈alkenyl-C(═O)—), C₁₋₁₀alkoxycarbonyl (C₁₋₁₀alkyl-O—C(═O)—),C₃₋₆cycloalkylcarbonyl (C₃₋₆cycloalkyl-C(═O)—) andC₃₋₆cycloalkyloxycarbonyl (C₃₋₆cycloalkyl-O—C(═O)—);

n is 0 or 1, wherein

-   -   when n is 1, X is ═O, and    -   when n is 0, a double bond exists between position 3 and        position 4 and X is selected from the group consisting of H, OH,        F, Cl, Br, I, C₁₋₆alkyl and NR₅R₆, where each of R₅ and R₆ is        independently selected from H and C₁₋₆ alkyl;

Z is selected from the group consisting of H, OH, F, Cl, Br, I,C₁₋₆alkyl and NR₅R₆, where each of R₅ and R₆ is independently selectedfrom H and C₁₋₆alkyl;

Y is selected from the group consisting of H, OH, F, Cl, Br, I,C₁₋₆alkyl, C₂₋₈alkynyl and NR₅R₆, where each of R₅ and R₆ isindependently selected from H and C₁₋₆alkyl;

Q is selected from the group consisting of O, S and CR₇R₈, where R₇ andR₈ are independently selected from H and C₁₋₆alkyl;

each of R₁ and R₂ is independently selected from H, and the groupconsisting of C₁₋₂₀alkyl, C₂₋₂₀alkenyl, C₁₋₂₀alkoxy,C₁₋₂₀alkoxyC₁₋₂₀alkyl, C₁₋₂₀alkoxyC₆₋₃₀aryl, C₂₋₂₀alkynyl,C₃₋₂₀cycloalkylC₆₋₃₀aryl, C₆₋₃₀aryloxy, C₅₋₂₀heterocyclyl, any of whichis optionally substituted; and

each of R₃ and R₄ is independently selected from H, and the groupconsisting of C₁₋₂₀alkyl, C₂₋₂₀alkenyl, C₁₋₂₀alkoxy,C₁₋₂₀alkoxyC₁₋₂₀alkyl, C₁₋₂₀alkoxyC₆₋₃₀aryl, C₂₋₂₀alkynyl,C₃₋₂₀cycloalkylC₆₋₃₀aryl, C₆₋₃₀aryloxy, C₅₋₂₀heterocyclyl, any of whichis optionally substituted, preferably R₃ is alkyl, more preferably R₃ isselected from the group consisting of methyl, ethyl, 2-propyl, n-propyl,cyclohexyl, 2-butyl and benzyl;

with the proviso that R₁ and R₄ can together comprise a —(CH₂)₃—alkylene chain;

and pharmaceutically acceptable salts, solvates and prodrugs thereof.

According to a further aspect of the present invention there is provideda compound of formula I for use in a method of treatment, suitably inthe prophylaxis or treatment of a viral infection, more suitably in theprophylaxis or treatment of hepatitis C virus.

According to a further aspect of the present invention there is providedthe use of a compound of formula I in the manufacture of a medicamentfor the prophylaxis or treatment of a viral infection, preferably amedicament for the prophylaxis or treatment of hepatitis C virus.

According to a further aspect of the present invention, there isprovided a method of prophylaxis or treatment of a viral infection,particularly hepatitis C virus, comprising administration to a patient,suitably a homo sapiens, in need of such treatment an effective dose ofa compound of formula I.

According to a further aspect of the present invention, there isprovided a pharmaceutical composition comprising a compound of formula Iin combination with a pharmaceutically acceptable carrier, diluent orexcipient.

According to a further aspect of the present invention there is provideda method of preparing a pharmaceutical composition comprising the stepof combining a compound of formula I with a pharmaceutically acceptableexcipient, carrier or diluent.

According to a further aspect of the present invention there is provideda process for the preparation of a compound of formula I, the processcomprising reacting a compound of formula III:

with a compound of formula IV:

where Ar, T, V, T″, n, X, Y, Z, Q, R₁, R₂, R₃ and R₄ have the meaningsset out above with respect to Formula I.

It is to be understood that the present invention extends to metabolicintermediates of compounds of formula I, wherein Ar is H and R₃ is H orR₃ is as defined above.

It is appreciated that having regard to the compounds defined above withrespect to Formulae I and III, a compound where n is 1 and X is ═O isthe keto tautomeric form of an otherwise equivalent enol compound wheren is 0 and X is OH.

The present invention particularly includes guanine as the base moietywhere n is 1, X is ═O, Y is NH₂ and no double bond exists betweenposition 3 and position 4 i.e. between the carbon ring atom bearing the═O and the adjacent ring nitrogen atom.

Compounds embodying the present invention have surprisingly been foundto have enhanced anti-viral activity. In particular, compounds embodyingthe present invention have been found to have enhanced potency withrespect to hepatitis C virus.

The enhanced anti-viral potency of the compounds of the presentinvention is believed to be due to the presence in the molecule offormula I of the combination of the fused multi-ring entity for Ar inthe phosphoramidate moiety and the methylene (—CH₂—) group at the β-2′position in the glycoside moiety of the nucleoside, with T, V and T″ asset out above.

By C₉₋₃₀aryl is meant an aromatic entity comprising 9 to 30 ring carbonatoms in an aryl format. By C₆₋₃₀heteroaryl is meant an aromatic entitycomprising 6 to 30 ring carbon atoms in an aryl format, with at leastone aryl ring containing a ring hetero atom.

Suitably, Ar can comprise two, three, four, five or six fused aromaticrings. Preferably, Ar comprises an aryl entity in the form of two orthree fused aromatic rings. More preferably, Ar is a two-ring fusedaromatic entity selected from C₉ to C₂₀ aryl and C₆ to C₂₀ heteroaryl.Where Ar is heteroaryl, suitably 1 to 12 hetero atoms are within thearyl rings and suitably are selected, independently, from 1 to 4nitrogen atoms, 1 to 4 oxygen atoms and 1 to 4 sulphur atoms.Preferably, the hetero atoms include nitrogen.

Available carbon atoms and/or heteroatoms in the aryl or heteroaryl ringsystem of Ar may be substituted on the ring with one or moresubstituents, as set out below with respect to the substituents that maybe present on the group Ar. Preferably Ar is unsubstituted.

Suitably, Ar is naphthyl (C₁₀H₇) or quinolyl (C₉H₆N), each of which maybe optionally substituted.

Most suitably, Ar is naphthyl. The naphthyl entity is preferably linkedto the O—P entity at the 1 or α position on the naphthyl group, i.e. ata C atom adjacent the fused bond between the two rings in the naphthylgroup. Any optional substituent is preferably present at the 4 position.Preferably Ar is unsubstituted 1-naphthyl.

When Ar is quinolyl, it is preferably linked to the O—P entity at the 4position on the quinolyl group, i.e. on the same ring as that containingthe hetero atom N, which N is numbered as position 1. Any substituentpresent is preferably present at the 6 position, i.e on the ring notcontaining the hetereo N atom, which N is numbered as position 1.

Preferably T is selected from the group consisting of hydrogen (H—),fluoro (F—), methyl (CH₃—) and ethyl (C₂H₅—).

Preferably V is selected from the group consisting of hydrogen (H—),fluoro (F—) and OT′, where T′ is hydrogen (H—) or methyl (CH₃—).

Preferably T″ is hydrogen (H—).

A preferred combination of T, V and T″ is T=H, V═OH and T″=H.

The combination of the above recited preferred entities for Ar with T=H,V═OH and T″=H is especially preferred.

Preferably n is 1 and X is ═O. More preferably n is 1, X is ═O and Y isNH₂ and the nucleoside base moiety corresponds to 9-linked guanine.Where Z is H, the nucleoside base moiety corresponds to unsubstituted9-linked guanine. Where Z is not H, the nucleoside base moietycorresponds to 8-substituted 9-linked guanine.

Alternatively, preferably n is 0 and X is selected from the groupconsisting of NH₂, F, Cl and NR₅R₆ where one of R₅ and R₆ is H and oneof R₅ and R₆ is C₁₋₆alkyl. Where n is 0, X is NH₂, Y is H and Z is H,the nucleoside base moiety corresponds to 9-linked adenine.

Preferably, Y is selected from the group consisting of H, F, Cl, NH₂ andNR₅R₆ where one of R₅ and R₆ is H and one of R₅ and R₆ is C₁₋₆alkyl.

Preferably, Z is selected from the group consisting of H, F and Cl.

Preferably, Q is O.

Preferably, R₃ is alkyl. More preferably, R₃ is selected from the groupconsisting of methyl (—CH₃), ethyl (CH₃CH₂—), 2-propyl ((CH₃)₂CH—),n-propyl (CH₃—CH₂—CH₂—), cyclohexyl (C₆H₁₁—), 2-butyl((CH₃)C(H)(CH₂CH₃)—) and benzyl (C₆H₅CH₂—), even more preferably R₃ isselected from the group consisting of methyl, ethyl, 2-propyl andbenzyl, even more preferably R₃ is selected from the group consisting ofethyl and benzyl.

Preferably, R₄ is H or, together with R₁, comprises (—(CH₂)₃—) so as toprovide a group corresponding to proline.

Preferably, R₁ and R₂ are independently selected from the groupconsisting of H, 2-propyl ((CH₃)₂CH—), benzyl (C₆H₅CH₂—) and—CH₂isopropyl ((CH₃)₂C(H)—CH₂—) or are selected such that theycorrespond to the side chains of a natural amino acid.

Preferably, one of R₁ and R₂ is methyl (—CH₃) and one of R₁ and R₂ is H,such that the C atom bearing R₁ and R₂ has chirality L as in naturalalanine.

Preferred compounds have in combination the preferred identities for Ar,T, V, T′, T″, X, Y, Z, Q, R₁, R₂, R₃ and R₄ as set out above.

Particularly preferred compounds have:

n=1, X══O, Y═NH₂, Z═H, Q=O, T=H, V═OH and T″=H and are thus derived fromguanine; and

n=0, X═NH₂, Y═Z═H, Q=O, T=H, V═OH and T″=H and are thus derived fromadenine.

Each of the particularly preferred compounds set out immediately aboveand so derived from guanine or adenine is especially preferred when eachof Ar, R₁, R₂, R₃ and R₄ has the preferred identities set out above, andis especially preferred when Ar is 1-naphthyl and R₃ is benzyl or ethyl.

Particularly preferred compounds are described in Examples 2, 3, 4, 6,7, 8 and 11 and set out in Table II below.

The phosphorus centre in compounds of formula I may be onediastereoisomer R_(P) or S_(P) or it may be a mixture of thediastereoisomers R_(P) or S_(P). Preferably it is one purediastereoisomer. Suitably the more active diastereoisomer is selected.

Suitably the pharmaceutical acceptable salts, solvates and prodrugs ofcompounds of formula I are esters or amides at the 3′-OH of theglycoside moiety of the nucleoside group.

Preferably the process for preparing the compound of formula I includesthe step of protecting free OH groups, other than 5′ on the glycosidemoiety of the nucleoside group. The phosphorochloridate may be preparedfrom an aryloxy phosphorodichloridate and a suitably protected aminoacid derivative. Alternatively, phosphate chemistry may be used withsuitable condensing agents.

Each of Ar, R₁, R₂, R₃ and R₄ can be substituted with one, two, three,four, five or more substituents independently selected from the groupcomprising electron donating and electron withdrawing moieties.

Substituents on Ar are suitably independently selected from the groupconsisting of hydroxy (OH—), acyl (R′C(═O)—), acyloxy (R′C(═O)O—), nitro(—NO₂), amino (—NH₂), —SO₃H, —SH, R′S—, wherein R′ is independentlyselected from the same group set out above as R₁; carboxyl (—COOH),C₁₋₆esters, C₁₋₆aldehyde, cyano (—CN), C₁₋₆alkylamino, C₁₋₆dialkylamino,thiol, chloro, bromo, fluoro, iodo, C₁₋₆alkyl, C₂₋₆alkenyl,C₁₋₆alkoxy-C₁₋₆alkyl, C₁₋₆alkoxy-C₅₋₁₀aryl, C₅₋₇cycloalkyl,C₅₋₁₁cycloalkyl-C₁₋₆alkyl, C₅₋₇cycloalkenyl, C₅₋₇cycloalkynyl,C₅₋₁₁arylC₁₋₆alkyl, C₁₋₆alkylC₅₋₁₁aryl, C₅₋₁₁aryl, C₁₋₆fluoroalkyl andC₂₋₆fluoroalkenyl. Each substituent can be substituted by any othersubstituent.

Substituents on R₁, R₂, R₃ and R₄ are independently selected from thegroup consisting of hydroxy (—OH), acyl (R′C(C═O)—), acyloxy(R′C(O═)O—), nitro (—NO₂), amino (—NH₂), amido (—CONH₂), —SO₃—H, —SH,—SR′, wherein R′ is independently selected from the same group set outabove as R₁, carboxyl (—COOH), C₁₋₆esters, C₁₋₆aldehyde, cyano (CN—),C₁₋₆alkylamino, C₁₋₆dialkylamino, thiol, chloro, bromo, fluoro, iodo,C₅₋₇cycloalkyl, C₅₋₇ cycloalkenyl, C₅₋₇cycloalkynyl, C₅₋₁₁aryl,C₅₋₁₁arylC₁₋₆alkyl and C₅₋₂₀heterocyclyl. Each substituent can besubstituted by any other substituent.

R₁ and R₂ are suitably independently selected from the group consistingof H, C₁₋₁₀alkyl, C₂₋₁₀alkenyl, C₂₋₁₀alkoxyC₁₋₁₀alkyl,C₁₋₁₀alkoxyC₆₋₁₀aryl, C₂₋₁₀alkynyl, C₃₋₂₀cycloalkyl, C₃₋₂₀cycloalkenyl,C₄₋₂₀cycloalkynyl, and C₅₋₁₀heterocyclyl.

R₁ and R₂ are suitably selected from the side chains of natural orsynthetic amino acids.

R₁ and/or R₂ are preferably a side chain of a natural amino acidselected from the group consisting of glycine, alanine, valine, leucine,isoleucine, phenylalanine, tyrosine, tryptophan, serine, threonine,lysine, arginine, histidine, aspartic acid, glutamic acid, asparagines,glutamine, cysteine and methionine. Specifically, R₁ and/or R₂ arepreferably selected from the group consisting of H, CH₃, —CH(CH₃)₂,—CH₂CH(CH₃)₂, —CH(CH₃)(CH₂CH₃), —CH₂Ph, —CH₂Ph-OH, —CH₂SH, —CH₂CH₂SCH₃,—CH₂OH, —CH(CH₃)(OH), —CH₂CH₂CH₂CH₂NH₃ ⁺, —CH₂CH₂CH₂NHC(═NH₂ ⁺)NH₂,—CH₂C(O)O—, —CH₂CH₂C(O)O—, —CH₂C(O)NH₂, —CH₂CH₂C(O)NH₂,

and wherein R₁ and R₄ together can form a 5-membered heterocyclic ringhaving the structure

R₃ and R₄ are suitably independently selected from the group consistingof H, C₁₋₁₀alkyl, C₂₋₁₀alkenyl, C₁₋₁₀alkoxy, C₁₋₁₀alkoxyC₁₋₁₀alkyl,C₁₋₁₀alkoxyC₆₋₁₀aryl, C₂₋₁₀alkynyl, C₃₋₂₀cycloalkyl, C₃₋₂₀cycloalkenyl,C₄₋₂₀cycloalkynyl, and C₅₋₂₀heterocyclyl.

R₃ is suitably selected from the group consisting of H, C₁₋₁₈alkyl,C₃₋₂₀cycloalkyl and benzyl.

R₄ is suitably selected from the group consisting of H, C₁₋₁₈alkyl,C₃₋₂₀cycloalkyl and C₅₋₂₀heterocyclyl. R₄ is particularly suitablyselected from the group consisting of H, methyl, ethyl, propyl, butyl,pentyl, hexyl and cyclohexyl.

In a preferred embodiment, R₁ and R₂ are methyl or are linked to form aclosed 5-membered heterocyclic or carbocyclic ring, for example, aspresent in proline.

As used herein, the term “alkyl” refers to a straight or branchedsaturated monovalent cyclic or acyclic hydrocarbon radical, having thenumber of carbon atoms as indicated (or where not indicated, an acyclicalkyl group preferably has 1-20, more preferably 1-6, more preferably1-4 carbon atoms and a cyclic alkyl group preferably has 3-20,preferably 3-10, more preferably 3-7 carbon atoms), optionallysubstituted with one, two, three or more substituents independentlyselected from the group set out above with respect to substituents thatmay be present on R₁, R₂, R₃ and R₄. By way of non-limiting examples,suitable alkyl groups include methyl, ethyl, propyl, butyl, pentyl,hexyl, octyl, nonyl and dodecyl.

As used herein, the term “alkenyl” refers to a straight or branchedunsaturated monovalent acyclic or cyclic hydrocarbon radical having oneor more C═C double bonds and having the number of carbon atoms asindicated (or where not indicated, an acyclic alkenyl group preferablyhas 2-20, more preferably 2-6, more preferably 2-4 carbon atoms and acyclic alkenyl group preferably has 4-20, more preferably 4-6 carbonatoms), optionally substituted with one, two, three or more substituentsindependently selected from the group set out above with respect tosubstituents that may be present on R₁, R₂, R₃ and R₄. By way ofnon-limiting examples, suitable alkenyl groups include vinyl, propenyl,butenyl, pentenyl and hexenyl.

As used herein, the term “alkynyl” refers to a straight or branchedunsaturated monovalent acyclic or cyclic hydrocarbon radical having oneor more triple C≡C bonds and having the number of carbon atoms asindicated (or where not indicated, an acyclic alkynyl group preferablyhas 2-20, more preferably 2-6, more preferably 2-4 carbon atoms and acyclic alkynyl group preferably has 7-20, more preferably 8-20 carbonatoms), optionally substituted with one, two, three or more substituentsindependently selected from the group set out above with respect tosubstituents that may be present on R₁, R₂, R₃ and R₄.

As use herein, the term “alkoxy” or the term “alkyloxy” refers to thegroup alkyl-O—, where alkyl is as defined above and where the alkylmoiety may optionally be substituted by one, two, three or moresubstituents as set out above for alkyl. By way of non-limitingexamples, suitable alkoxy groups include methoxy, ethoxy, n-propoxy,iso-propoxy, n-butoxy, tert-butoxy, sec-butoxy, n-pentoxy, n-hexoxy and1,2-dimethylbutoxy. The term “cycloalkyloxy” refers to the groupcyclicalkyl-O—, where cyclicalkyl is as defined above and where thecyclicalkyl moiety may be optionally substituted by one, two, three ormore substituents as set out above for alkyl.

As used herein, the term “aryloxy” refers to the group aryl-O—, wherearyl is as defined below and where the aryl moiety may optionally besubstituted by one, two, three or more substituents as set out abovewith respect to the group Ar.

As used herein, the term “alkoxyalkyl” refers to an alkyl group havingan alkoxy substituent. Binding is through the alkyl group. The alkylmoiety and the alkoxy moiety are as defined herein with respect to thedefinitions of alkyl and alkoxy, respectively. The alkoxy and alkylmoieties may each be substituted by one, two, three or more substituentsas set out above with regard to the definition of alkyl.

As used herein, the term “alkoxyaryl” refers to an aryl group having analkoxy substituent. Binding is through the aryl group. The alkoxy moietyand the aryl moiety are as defined herein with respect to thedefinitions of alkoxy and aryl, respectively. The alkoxy and arylmoieties may each be substituted by one, two, three or moresubstituents, as defined herein with regard to the definitions of alkoxyand aryl, respectively.

As used herein, the term “cycloalkylaryl” refers to an aryl group havinga cyclic alkyl substitutent. Binding is through the aryl group. Thecycloalkyl moiety and the aryl moiety are as defined herein with respectto the definitions of cycloalkyl and aryl, respectively. The cycloalkylmoiety and the aryl moiety may each be optionally substituted by one,two, three or more substituents as set out herein with regard to thedefinitions of alkyl and aryl, respectively.

Except where otherwise stated with respect to the definition of “Ar”, asused herein the term “aryl” refers to a monovalent unsaturated aromaticcarbocyclic radical having one, two, three, four, five or six rings,preferably one, two or three rings, which may be fused or bicyclic. Anaryl group may optionally be substituted by one, two, three or moresubstituents as set out above with respect to optional substituents thatmay be present on the group Ar. Preferred aryl groups are: an aromaticmonocyclic ring containing 6 carbon atoms; an aromatic bicyclic or fusedring system containing 7, 8, 9 or 10 carbon atoms; or an aromatictricyclic ring system containing 10, 11, 12, 13 or 14 carbon atoms.Non-limiting examples of aryl include phenyl and naphthyl. Preferredsubstituent groups are independently selected from hydroxy (—OH), acylacyloxy (R′—C(═O)—), acyloxy (R′—C(═O)—O—), nitro (—NO₂), amino (—NH₂),—SO₃H, —SH, —SR′, wherein R′ is independently selected from the samegroups as R₁; carboxyl (—COOH), cyano (—CN), C₁₋₆alkylamino,C₁₋₆dialkylamino, thiol, chloro, bromo, fluoro and iodo.

As used herein, the term “heterocyclyl” refers to a saturated orpartially unsaturated heterocyclic ring system having one, two, three,four, five or six rings, preferably one, two or three rings, which maybe fused or bicyclic, and having contained within the ring or rings atleast one member selected from the group consisting of N, O and S. Theprefix “C₅₋₂₀” or “C₅₋₁₀” used before heterocyclyl means, respectively,a five to twenty or a five to ten membered ring system at least one ofwhich members is selected from the group consisting of N, O and S.Preferred heterocyclyl systems are: a monocyclic ring system having fivemembers of which at least one member is a N, O or S atom and whichoptionally contains one additional O atom or one, two or threeadditional N atoms; a monocyclic ring having six members of which one,two or three members are a N atom; a bicyclic ring system having ninemembers of which at least one member is a N, O or S atom and whichoptionally contains one, two or three additional N atoms; or a bicyclicring system having ten members of which one, two or three members are aN atom. Examples include, and are not limited to, pyrrolinyl,pyrrolidinyl, 1,3-dioxolanyl, imidazolinyl, imidazolidinyl, pyrazolinyl,pyrazolidinyl, piperidinyl, morpholinyl or piperazinyl.

Available carbon atoms and/or heteroatoms of the “heterocyclyl” ringsystems described above may be substituted on the ring with one or moreheteroatoms. Where the ring(s) is substituted with one or moreheteroatoms selected from oxygen, nitrogen and sulphur, and the ring(s)may include other substituents such as halogen (F, Cl, Br and I). Wherethe ring(s) is substituted with one or more heteroatoms, preferablythere are one or more heteroatom substituents selected from the groupconsisting of oxygen, nitrogen and/or sulphur. Preferred substituentgroups are independently selected from hydroxy, acyl, acyloxy, nitro,amino, SO.sub.3H, SH, SR′, wherein R′ is independently selected from thesame groups as R; carboxyl, cyano, C.sub.1-6alkylamino,C.sub.1-6dialkylamino, thiol, chloro, bromo, fluoro and iodo.

The process is preferably carried out in the presence of a suitablesolvent.

Suitable solvents include hydrocarbon solvents such as benzene andtoluene; ether type solvents such as diethyl ether, tetrahydrofuran,diphenyl ether, anisole and dimethoxybenzene; halogenated hydrocarbonsolvents such as methylene chloride, chloroform and chlorobenzene;ketone type solvents such as acetone, methyl ethyl ketone and methylisobutyl ketone; alcohol type solvents such as methanol, ethanol,propanol, isopropanol, n-butyl alcohol and tert-butyl alcohol; nitriletype solvents such as acetonitrile, propionitrile and benzonitrile;ester type solvents such as ethyl acetate and butyl acetate; carbonatetype solvents such as ethylene carbonate and propylene carbonate; andthe like. These may be used singly or two or more of them may be used inadmixture.

Preferably an inert solvent is used in the process of the presentinvention. The term “inert solvent” means a solvent inert under theconditions of the reaction being described in conjunction therewithincluding, for example, benzene, toluene, acetonitrile, tetrahydrofuran,dimethylformamide, chloroform, methylene chloride (or dichloromethane),diethyl ether, ethyl acetate, acetone, methylethyl ketone, methanol,ethanol, propanol, isopropanol, tert-butanol, dioxane, pyridine, and thelike. Tetrahydrofuran is particularly preferred.

Preferably the process of the present invention is carried out undersubstantially dry conditions.

As used herein, the term “stereoisomer” defines all possible compoundsmade up of the same atoms bonded by the same sequence of bonds buthaving different three-dimensional structures which are notinterchangeable, which the compounds of the present invention maypossess.

Where the compounds according to this invention have at least one chiralcenter, they may accordingly exist as enantiomers. Where the compoundspossess two or more chiral centers, they may additionally exist asdiastereomers. Where the processes for the preparation of the compoundsaccording to the invention give rise to mixture of stereoisomers, theseisomers may be separated by conventional techniques such as preparativechromatography. The compounds may be prepared in stereochemically mixedform or individual enantiomers may be prepared by standard techniquesknown to those skilled in the art, for example, by enantiospecificsynthesis or resolution, formation of diastereomeric pairs by saltformation with an optically active acid, followed by fractionalcrystallization and regeneration of the free base. The compounds mayalso be resolved by formation of diastereomeric esters or amides,followed by chromatographic separation and removal of the chiralauxiliary. Alternatively, the compounds may be resolved using a chiralHPLC column. It is to be understood that all such isomers and mixturesthereof are encompassed within the scope of the present invention.

Furthermore, it should be appreciated that the phosphate centre ischiral in the compounds of the present invention and the compounds mayexist as Rp and Sp diastereoisomers. The composition of the compound maybe mixed Rp and Sp or one pure diastereomer. Preferably the compound isa substantially pure single isomer.

There may be a mixture of 1:1 Rp to Sp diastereomers. Alternatively,there may be a ratios of 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10,1:15, 1:20, 1:50 or 1:100 of Rp to Sp diastereomers or vice versa.

The term “solvate” means a compound of as defined herein, or apharmaceutically acceptable salt of a compound of structure (I) or (II),wherein molecules of a suitable solvent are incorporated in the crystallattice. A suitable solvent is physiologically tolerable at the dosageadministered. Examples of suitable solvents are ethanol, water and thelike. When water is the solvent, the molecule is referred to as ahydrate.

The compounds of the present invention may also be present in the formof pharmaceutical acceptable salts. For use in medicine, the salts ofthe compounds of this invention refer to non-toxic “pharmaceuticallyacceptable salts.” FDA approved pharmaceutical acceptable salt forms(Ref. International J. Pharm. 1986, 33, 201-217; J. Pharm. Sci., 1977,January, 66 (1)) include pharmaceutically acceptable acidic/anionic orbasic/cationic salts.

Pharmaceutically acceptable acidic/anionic salts include, and are notlimited to acetate, benzenesulfonate, benzoate, bicarbonate, bitartrate,bromide, calcium edetate, camsylate, carbonate, chloride, citrate,dihydrochloride, edetate, edisylate, estolate, esylate, fumarate,glyceptate, gluconate, glutamate, glycollylarsanilate, hexylresorcinate,hydrabamine, hydrobromide, hydrochloride, hydroxynaphthoate, iodide,isethionate, lactate, maleate, mandelate, mesylate, methylbromide,methylnitrate, methylsulfate, mucate, napsylate, nitrate, pamoate,pantothenate, phosphate, diphospate, polygalacturonate, salicylate,stearate, subacetate, succinate, sulfate, tannate, tartrate, teoclate,tosylate and triethiodide.

Pharmaceutically acceptable basic/cationic salts include, and are notlimited to aluminum, benzathine, calcium, chloroprocaine, choline,diethanolamine, ethylenediamine, lithium, magnesium, potassium,procaine, sodium and zinc.

The present invention includes within its scope prodrugs of thecompounds of this invention. In general, such prodrugs will befunctional derivatives of the compounds which are readily convertible invivo into the required compound. Thus, in the methods of treatment ofthe present invention, the term “administering” shall encompass thetreatment of the various disorders described with the compoundspecifically disclosed or with a compound which may not be specificallydisclosed, but which converts to the specified compound in vivo afteradministration to the subject. Conventional procedures for the selectionand preparation of suitable prodrug derivatives are described, forexample, in “Design of Prodrugs”, ed. H. Bundgaard, Elsevier, 1985.

Pharmaceutically acceptable ester derivatives in which one or more freehydroxy groups are esterified in the form of a pharmaceuticallyacceptable ester are particularly prodrug esters that may be convertibleby solvolysis under physiological conditions to the compounds of thepresent invention having free hydroxy groups.

Pharmaceutical compositions for use in accordance with the presentinvention may be formulated in a conventional manner using one or morephysiologically acceptable carriers comprising excipients andauxiliaries which facilitate processing of the active compounds intopreparations which can be used pharmaceutically. These pharmaceuticalcompositions may be manufactured in a manner that is itself known, e.g.,by means of conventional mixing, dissolving, granulating, dragee-making,levigating, emulsifying, encapsulating, entrapping or lyophilizingprocesses. Proper formulation is dependent upon the route ofadministration chosen.

The compound having formula I or pharmaceutical composition according tothe present invention can be administered to a patient, which may behomo sapiens or animal, by any suitable means.

The medicaments employed in the present invention can be administered byoral or parenteral routes, including intravenous, intramuscular,intraperitoneal, subcutaneous, transdermal, airway (aerosol), rectal,vaginal and topical (including buccal and sublingual) administration.

For oral administration, the compounds of the invention will generallybe provided in the form of tablets or capsules, as a powder or granules,or as an aqueous solution or suspension.

Tablets for oral use may include the active ingredient mixed withpharmaceutically acceptable excipients such as inert diluents,disintegrating agents, binding agents, lubricating agents, sweeteningagents, flavouring agents, colouring agents and preservatives. Suitableinert diluents include sodium and calcium carbonate, sodium and calciumphosphate, and lactose, while cornstarch and alginic acid are suitabledisintegrating agents. Binding agents may include starch and gelatin,while the lubricating agent, if present, will generally be magnesiumstearate, stearic acid or talc. If desired, the tablets may be coatedwith a material such as glyceryl monostearate or glyceryl distearate, todelay absorption in the gastrointestinal tract.

Capsules for oral use include hard gelatin capsules in which the activeingredient is mixed with a solid diluent, and soft gelatin capsuleswherein the active ingredient is mixed with water or an oil such aspeanut oil, liquid paraffin or olive oil.

Formulations for rectal administration may be presented as a suppositorywith a suitable base comprising for example cocoa butter or asalicylate.

Formulations suitable for vaginal administration may be presented aspessaries, tampons, creams, gels, pastes, foams or spray formulationscontaining in addition to the active ingredient such carriers as areknown in the art to be appropriate.

For intramuscular, intraperitoneal, subcutaneous and intravenous use,the compounds of the invention will generally be provided in sterileaqueous solutions or suspensions, buffered to an appropriate pH andisotonicity. Suitable aqueous vehicles include Ringer's solution andisotonic sodium chloride. Aqueous suspensions according to the inventionmay include suspending agents such as cellulose derivatives, sodiumalginate, polyvinyl-pyrrolidone and gum tragacanth, and a wetting agentsuch as lecithin. Suitable preservatives for aqueous suspensions includeethyl and n-propyl p-hydroxybenzoate.

The compounds of the invention may also be presented as liposomeformulations.

In general a suitable dose will be in the range of 0.1 to 300 mg perkilogram body weight of the recipient per day. A preferred lower dose is0.5 mg per kilogrm body weight of recipient per day, a more preferredlower dose is 1 mg per kilogram body weight of recipient per day. Asuitable dose is preferably in the range of 1 to 50 mg per kilogram bodyweight per day, and more preferably in the range of 1 to 10 mg perkilogram body weight per day. The desired dose is preferably presentedas two, three, four, five or six or more sub-doses administered atappropriate intervals throughout the day. These sub-doses may beadministered in unit dosage forms, for example, containing 10 to 1500mg, preferably 20 to 1000 mg, and most preferably 50 to 700 mg of activeingredient per unit dosage form.

EXAMPLES

Embodiments of the present invention will now be described by way ofexample only with respect to the following examples.

Target compounds were prepared by reacting the appropriate nucleoside,or its modified precursor, with the required phosphorochloridate. Thelatter reagents were prepared by published methods from arylphosporodichloridates with amino acid ester hydrochlorides. Severalexamples are given.

Standard Procedure C2 Preparation of2′,3′-cyclopentylidyn-modified-nucleoside phosphoramidates

^(t)BuMgCl (2.0 mol. equivalent) and 2′,3′-cyclopentylidene,4′-azido-cytidine (1.0 mol. equivalent) were dissolved in drytetrahydrofuran (THF) (31 mol. equivalent) and stirred for 15 minutes.Then a 1M solution of the appropriate phosphorochloridate (2.0 mol.equivalent) in dry THF was added dropwise, then stirred overnight. Asaturated solution of NH₄Cl was added and the solvent was removed underreduced pressure to give a yellow solid, which was consequentlypurified.

Standard Procedure C3 Preparation of phosphoramidates of ModifiedNucleoside

2′,3′-cyclopentylidene, modified nucleoside phosphoramidates weredissolved in a solution 80% of formic acid in water for 4 hours. Thesolvent was removed under reduced pressure to give a white solid whichwas consequently purified.

Standard Procedure C4 Preparation of phosphoramidates of ModifiedNucleoside

2′,3′-isopropilidene, modified nucleoside phosphoramidates weredissolved in a solution 60% of acetic acid in water at 90° C. overnight.The solvent was removed under reduced pressure to give a white solidwhich was consequently purified.

Example 1 Synthesis of β-2′-methyl-adenosine (CHC1)

N6-tert-butanoyl-β-2′-methyl-2′,3′,5′-tribenzoyl-adenosine (400 mg,0.590 mmol) was added to a solution of MeOH saturated with ammonia, andstirred at room temperature. After 12 hours the solvent was removed andthe obtained solid was purified by column chromatography in gradientstarting with a mixture of CHCl₃/MeOH 9:1 then 8:2. The pure product wasobtained as a white solid (120 mg, 0.427 mmol, 72%).

δ_(H) (d₆-DMSO): 8.47 (1H, s, H8-adenosine), 8.15 (1H, s, H2-adenosine),7.30 (1H, s, NH₂6-adenosine), 5.95 (1H, s, H1′-adenosine), 5.25-5.21(3H, m, OH5′-adenosine, OH3′-adenosine, OH2′-adenosine), 4.12-4.05 (1H,d, H3′-adenosine, J=8.6 Hz), 3.91 (1H, m, H4′-adenosine), 3.84 (1H, m,H5′-adenosine), 3.70 (1H, m, H5′-adenosine), 0.77 (3H, s,CH₃2′-adenosine); δ_(C) (d₆-DMSO): 156.02 (1C, C6-adenosine), 152.53(1C, C2-adenosine), 149.01 (1C, C4-adenosine), 138.68 (1C,C8-adenosine), 118.67 (1C, C5-adenosine), 90.78 (1C, C1′-adenosine),82.52 (1C, C4′-adenosine), 78.46 (1C, C2′-adenosine), 71.63 (1C,C3′-adenosine), 59.47 (1C, C5′-adenosine), 19.83 (1C, CH₃-2′-adenosine).Anal. Calc. for C₁₁H₁₅N₅O₄: C 46.97%, H 5.38%, N 24.90%. Found: C46.67%, H 5.22%, N 24.20%.

Example 2 Synthesis of 2′,3′-O,O-cyclopentylidyn-β-2′-methyl-adenosine5′-O-[phenyl(ethoxy-L-alaninyl]phosphate

Prepared according to Standard Procedure C2, from2′,3′-O,O-cyclopentylidyn-β-2′-methyl-adenosine (60 mg, 0.172 mmol),^(t)BuMgCl (0.5 ml, 1M solution in THF, 0.519 mmol) andα-naphthyl(ethoxy-L-alaninyl)phosphorochloridate (0.5 ml of solution 1Min THF, 0.519 mmol). The crude was purified by column chromatography,using as eluent CHCl₃/MeOH (95:5). The obtained pure product was a whitesolid (30 mg, 0.046 mmol, 26%).

δ_(P)) (d₄-CH₃OH): 4.31, 4.26; δ_(H) (d₄-CH₃OH): 8.19 (1H, s,H2-adenosine), 8.10 (1H, s, H8-adenosine), 7.88 (1H, m, CH-naphthyl),7.73 (1H, m, CH-naphthyl), 7.57-7.52 (4H, m, CH-naphthyl), 7.45-7.43(1H, m, CH-naphthyl), 6.26 (1H, m, H1′-adenosine), 4.56-4.42 (4H, m,H4′-adenosine, H3′-adenosine, 2H5′-adenosine), 4.08 (3H, m, CHα,CH₂-ethyl), 2.21-2.09 (2H, m, CH₂-cyclopentyl), 1.76-1.71 (6H, m, 3CH₂-cyclopentyl), 1.35 (3H, d, CH₃-alanine, J=6.9 Hz), 1.25 (3H, m,CH₃-ethyl), 0.95 (3H, s, CH₃2′-adenosine).

Synthesis of β-2′-methyl-adenosine5′-O-[α-naphthyl(ethoxy-L-alaninyl)]phosphate (CHC2)

Prepared according to Standard Procedure C3, from2′,3′-O,O-cyclopentylidyn-β-2′-methyl-adenosine5′-O-[α-naphthyl(ethoxy-L-alaninyl)]phosphate (30 mg, 0.036 mmol), and10 ml of a solution 80% of HCOOH in water. The crude was purified bycolumn chromatography, using as eluent for the first CHCl₃/MeOH (95:5)followed by a semi-preparative HPLC. The obtained pure product was awhite solid (4 mg, 0.007 mmol, 19%).

δ_(P) (d₄-CH₃OH): 4.23, 4.20; δ_(H) (d₄-CH₃OH): 8.24-8.19 (3H, m,H2-adenosine, H8-adenosine, CH-naphthyl), 7.90 (1H, m, CH-naphthyl),7.63 (1H, CH-naphthyl), 7.53 (4H, m, CH-naphthyl), 7.41 (1H, m,CH-naphthyl), 6.12 (1H, d, H1′-adenosine, J=2.1 Hz), 4.61-4.59 (2H, d,H3′-adenosine, H4′-adenosine), 4.30 (1H, m, H5′-adenosine), 4.02-3.99(3H, m, CHα, CH₂-ethyl), 1.37 (3H, m, CH₃-alanine), 1.27 (3H, m,CH₃-ethyl), 0.95 (3H, s, CH₃-2′-adenosine).

MS (ES) m/e: 609.2 (MNa⁺, 100%); Accurate mass: C₂₆H₃₁N₆O₈NaP required609.1846, found 609.1839.

Example 3 Synthesis of 2′,3′-O,O-cyclopentylidyn-β-2′-methyl-adenosine5′-O-[phenyl(benzoxy-L-alaninyl)]phosphate

Prepared according to Standard Procedure C2, from2′,3′-O,O-cyclopentylidyn-β-2′-methyl-adenosine (40 mg, 0.115 mmol),^(t)BuMgCl (0.35 ml, 1M solution in THF, 0.345 mmol) andα-naphthyl(benzoxy-L-alaninyl)phosphorochloridate (0.35 ml of solution1M in THF, 0.345 mmol). The crude was purified by column chromatography,using as eluent CHCl₃/MeOH (95:5). The obtained pure product was a whitesolid (20 mg, 0.028 mmol, 24%).

δ_(P) (d₄-CH₃OH): 4.34, 4.18; δ_(H) (d₄-CH₃OH): 8.50 (1H, s,H2-adenosine), 8.17 (1H, s, H8-adenosine), 7.90 (1H, m, CH-naphthyl),7.71 (1H, m, CH-naphthyl), 7.69 (1H, CH-benzyl), 7.55-7.50 (3H, m,CH-naphthyl, 2 CH-benzyl), 7.42-7.27 (6H, m, 4 CH-naphthyl, 2CH-benzyl), 6.25 (1H, d, H1′-adenosine), 5.10 (2H, s, CH₂-benzyl), 4.61(1H, m, H3′-adenosine), 4.41 (1H, m, H4′-adenosine), 4.15 (1H, m, CHα),3.95 (1H, m, H5′-adenosine, J=12.2 Hz), 3.85 (1H, m, H5′-adenosine,J=12.2 Hz), 2.12-2.03 (2H, m, CH₂-cyclopentyl), 1.79-1.72 (6H, m, 3CH₂-cyclopentyl), 1.37 (3H, d, CH₃-alanine, J=7.2 Hz), 0.89 (3H, s,CH₃-2′-adenosine).

Synthesis of β-2′-methyl-adenosine5′-O-[α-naphthyl(benzoxy-L-alaninyl)]phosphate (CHC3)

Prepared according to Standard Procedure C3, from2′,3′-O,O-cyclopentylidyn-β-2′-methyl-adenosine5′-O-[α-naphthyl(benzoxy-L-alaninyl)]phosphate (30 mg, 0.036 mmol), and10 ml of a solution 80% of HCOOH in water. The crude was purified bycolumn chromatography, using as eluent for the first CHCl₃/MeOH (95:5)followed by a semi-preparative HPLC. The obtained pure product was awhite solid (5 mg, 0.008 mmol, 21%).

δ_(P) (d₄-CH₃OH): 4.25, 4.14; δ_(H) (d₄-CH₃OH): 8.04-7.95 (3H, m,H2-adenosine, H8-adenosine, CH-naphthyl), 7.68 (1H, m, CH-naphthyl),7.48 (1H, m, CH-naphthyl), 7.32-7.23 (3H, m, CH-naphthyl, 2 CH-benzyl),7.16 (1H, m, CH-naphthyl), 7.05 (6H, m, 3 CH-naphthyl, 3 CH-benzyl),5.88 (1H, d, H1′-adenosine, J=2.9 Hz), 4.85-4.65 (2H, m, CH₂-benzyl),4.37-4.35 (2H, d, H3′-adenosine, H4′-adenosine), 4.06 (2H, m,H5′-adenosine), 3.88-3.83 (1H, m, CHα), 1.35 (3H, m, CH₃-alanine), 0.88(3H, s, CH₃-2′-adenosine).

MS (ES) m/e: 671.2 (MNa⁺, 100%); Accurate mass: C₃₁H₃₃N₆O₈NaP required671.1990, found 671.1995.

Example 4 Synthesis of 2′,3′-O,O-cyclopentylidyn-β-2′-methyl-adenosine5′-O-[phenyl(tert-butoxy-L-alaninyl)]phosphate

Prepared according to Standard Procedure C2, from2′,3′-O,O-cyclopentylidyn-β-2′-methyl-adenosine (60 mg, 0.172 mmol),^(t)BuMgCl (0.51 ml, 1M solution in THF, 0.51 mmol) andα-naphthyl(tert-butoxy-L-alaninyl)phosphorochloridate (0.5 ml ofsolution 1M in THF, 0.519 mmol). The crude was purified by columnchromatography, using as eluent CHCl₃/MeOH (95:5). The obtained pureproduct was a white solid (27 mg, 0.039 mmol, 22%).

δ_(P) (d₄-CH₃OH): 4.37, 4.28; δ_(H) (d₄-CH₃OH): 8.21 (1H, s,H2-adenosine), 8.13 (1H, s, H8-adenosine), 7.85 (1H, m, CH-naphthyl),7.73 (1H, m, CH-naphthyl), 7.57-7.52 (4H, m, CH-naphthyl), 7.43-7.41(1H, m, CH-naphthyl), 6.25 (1H, m, H1′-adenosine), 4.55-4.40 (4H, m,H4′-adenosine, H3′-adenosine, 2H5′-adenosine), 4.05 (1H, m, CHα),2.20-2.12 (2H, m, CH₂-cyclopentyl), 1.79-1.69 (6H, m, 3CH₂-cyclopentyl), 1.36 (9H, 3 CH₃-tert-butyl), 1.25 (3H, d, CH₃-alanine,J=6.9 Hz), 0.96 (3H, s, CH₃-2′-adenosine).

Synthesis of β-2′-methyl-adenosine5′-O-[α-naphthyl(tert-butoxy-L-alaninyl)]phosphate (CHC4)

Prepared according to Standard Procedure C3, from2′,3′-O,O-cyclopentylidyn-β-2′-methyl-adenosine5′-O-[α-naphthyl(tert-butoxy-L-alaninyl)]phosphate (27 mg, 0.039 mmol),and 10 ml of a solution 80% of HCOOH in water. The crude was purified bycolumn chromatography, using as eluent for the first CHCl₃/MeOH (95:5)followed by a semi-preparative HPLC. The obtained pure product was awhite solid (10 mg, 0.016 mmol, 41%).

δ_(P) (d₄-CH₃OH): 4.20, 4.08; δ_(H) (d₄-CH₃OH): 8.20-8.15 (3H, m,H2-adenosine, H8-adenosine, CH-naphthyl), 7.81 (1H, m, CH-naphthyl),7.60 (1H, CH-naphthyl), 7.54 (4H, m, CH-naphthyl), 7.39 (1H, m,CH-naphthyl), 6.15 (1H, d, H1′-adenosine), 4.63-4.57 (2H, d,H3′-adenosine, H4′-adenosine), 4.31 (1H, m, H5′-adenosine), 4.00-3.97(1H, m, CHα), 1.39 (9H, 3 CH₃-tert-butyl), 1.27 (3H, m, CH₃-alanine),0.97 (3H, s, CH₃-2′-adenosine).

Example 5 Synthesis of β-2′-methyl-guanosine (CHC5)

N2-acetyl-β-2′-methyl-2′,3′,5′-tribenzoyl-guanosine (1.42 g, 2.18 mmol)was added to a solution of MeOH saturated with ammonia, and stirred atroom temperature. After 12 hours the solvent was removed and theobtained solid was purified by column chromatography using as eluent amixture of CHCl₃/MeOH 8:2. The pure product was obtained as a whitesolid (565 mg, 1.90 mmol, 87%).

δ_(H) (d₆-DMSO): 10.52 (1H, s, NH1-guanosine), 8.48 (1H, s,H8-guanosine), 6.52 (2H, s, NH₂2-guanosine), 5.73 (1H, s,H1′-guanosine), 5.24 (1H, d, OH3′-guanosine, J=6.3 Hz), 5.11 (1H, m,OH5′-guanosine), 5.03 (1H, s, OH2′-guanosine), 3.97 (1H, m,H3′-guanosine), 3.85-3.79 (2H, m, H4′, H5′-guanosine), 3.66 (1H, d,H5′-guanosine, J=12.2 Hz), 0.81 (3H, s, CH₃-2′-guanosine); δ_(C)(d₆-DMSO): 156.72 (1C, C6-guanosine), 153.68 (1C, C2-guanosine), 150.77(1C, C4-guanosine), 135.07 (1C, C8-guanosine), 116.38 (1C,C5-guanosine), 90.10 (1C, C1′-guanosine), 82.30 (1C, C3′-guanosine),78.52 (1C, C2′-guanosine), 71.63 (1C, C4′-guanosine), 59.40 (1C,C5′-guanosine), 19.96 (1C, CH₃-2′-guanosine).

MS (ES) m/e: 320.2 (MNa⁺, 100%); Accurate mass: C₁₁H₁₅N₅O₅Na required320.0968, found 320.0971.

Example 6 Synthesis of 2′,3′-O,O-isopropylidyn-β-2′-methyl-guanosine5′-O-[phenyl(benzoxy-L-alaninyl)]phosphate

Prepared according to Standard Procedure C2, from2′,3′-O,O-isopropylidyn-β-2′-methyl-guanosine (170 mg, 0.503 mmol),^(t)BuMgCl (1.0 ml, 1M solution in THF, 1.006 mmol) andα-naphthyl(benzoxy-L-alaninyl)phosphorochloridate (1.0 ml of solution 1Min THF, 1.006 mmol). The crude was purified by column chromatography,using as eluent CHCl₃/MeOH (95:5). The obtained pure product was a whitesolid (70 mg, 0.098 mmol, 19%).

δ_(P) (d₄-CH₃OH): 4.53, 4.40; δ_(H) (d₄-CH₃OH): 8.28 (1H, s,H8-guanosine), 7.84 (1H, m, CH-naphthyl), 7.77-7.71 (1H, m, CH-benzyl),7.55-7.49 (4H, m, 2 CH-naphthyl, 2 CH-benzyl), 7.44-7.29 (6H, m, 4CH-naphthyl, 2 CH-benzyl), 6.06 (1H, d, H1′-guanosine), 5.10 (2H, s,CH₂-benzyl), 4.59 (1H, m, H3′-guanosine), 4.52-4.45 (1H, m,H4′-guanosine), 4.34 (2H, H5′ guanosine), 4.14 (1H, m, CHα), 1.59 (3H,d, CH₃-isopropylidine, J=10.4 Hz), 1.37 (6H, d, CH₃-alanine,CH₃-isopropylidine), 0.99 (3H, d, CH₃-2′-guanosine, J=20.11 Hz).

Synthesis of β-2′-methyl-guanosine5′-O-[α-naphthyl(benzoxy-L-alaninyl)]phosphate (CHC6)

Prepared according to Standard Procedure C4, from2′,3′-O,O-isopropylidyn-β-2′-methyl-guanosine5′-O[α-naphthyl(benzoxy-L-alaninyl)]phosphate (70 mg, 0.098 mmol), and10 ml of a solution 60% of CH₃COOH in water at 90° C. for 15 hours. Thecrude was purified by column chromatography, using as eluent for thefirst CHCl₃/MeOH (85:5) followed by a semi-preparative HPLC. Theobtained pure product was a white solid (12 mg, 0.018 mmol, 18%).

δ_(P) (d₄-CH₃OH): 4.25, 4.14; δ_(H) (d₄-CH₃OH): 8.17 (1H, m,H8-guanosine), 7.88 (1H, m, CH-naphthyl), 7.79 (1H, m, CH-naphthyl),7.53 (2H, m, CH-naphthyl, CH-benzyl), 7.42-7.40 (1H, m, CH-naphthyl),7.36-7.21 (7H, m, 3 CH-naphthyl, 4 CH-benzyl), 6.05 (1H, d,H1′-guanosine, J=8.4 Hz), 5.15-4.90 (2H, m, CH₂-benzyl), 4.58-4.49 (2H,d, H3′-guanosine, H4′-guanosine), 4.44-4.34 (2H, m, H5′-guanosine),4.17-4.11 (1H, m, CHα), 1.37 (3H, m, CH₃-alanine), 1.00 (3H, s,CH₃-2′-guanosine).

MS (ES) m/e: 687.2 (MNa⁺, 100%); Accurate mass: C₃₁H₃₃N₆O₉NaP required687.1954, found 687.1944.

Example 7 Synthesis of 2′,3′-O,O-isopropylidyn-β-2′-methyl-guanosine5′-O-[phenyl(ethoxy-L-alaninyl)]phosphate

Prepared according to Standard Procedure C2, from2′,3′-O,O-isopropylidyn-β-2′-methyl-guanosine (220 mg, 0.652 mmol),^(t)BuMgCl (1.3 ml, 1M solution in THF, 1.30 mmol) andα-naphthyl(ethoxy-L-alaninyl)phosphorochloridate (1.3 ml of solution 1Min THF, 1.30 mmol). The crude was purified by column chromatography,using as eluent CHCl₃/MeOH (95:5). The obtained pure product was a whitesolid (35 mg, 0.054 mmol, 9%).

δ_(P) (d₄-CH₃OH): 4.41, 4.32; δ_(H) (d₄-CH₃OH): 8.18 (1H, s,H8-guanosine), 7.88 (1H, m, CH-naphthyl), 7.73 (1H, m, CH-naphthyl),7.59-7.52 (4H, m, 4 CH-naphthyl), 7.46-7.42 (1H, m, CH-naphthyl), 6.08(1H, d, H1′-guanosine), 4.62-4.40 (4H, m, H3′-guanosine, H4′-guanosine,H5′guanosine), 4.11-4.09 (3H, m, CHα, CH₂-ethyl), 1.59 (3H, d,CH₃-isopropylidine, J=13.2 Hz), 1.37 (6H, m, CH₃-alanine,CH₃-isopropylidine), 1.20 (3H, m, CH₃-ethyl), 1.00 (3H, m,CH₃-2′-guanosine).

Synthesis of β-2′-methyl-guanosine5′-O-[α-naphthyl(ethoxy-L-alaninyl)]phosphate (CHC7)

Prepared according to Standard Procedure C4, from2′,3′-O,O-isopropylidyn-β-2′-methyl-guanosine5′-O-[α-naphthyl(ethoxy-L-alaninyl)]phosphate (35 mg, 0.054 mmol), and10 ml of a solution 60% of CH₃COOH in water at 90° C. for 15 hours. Thecrude was purified by column chromatography, using as eluent for thefirst CHCl₃/MeOH (85:5) followed by a semi-preparative HPLC. Theobtained pure product was a white solid (10 mg, 0.018 mmol, 31%).

δ_(P) (d₄-CH₃OH): 4.25, 4.14; δ_(H) (d₄-CH₃OH): 8.18 (1H, m,H8-guanosine), 7.87 (1H, m, CH-naphthyl), 7.71 (1H, m, CH-naphthyl),7.53 (4H, m, 4 CH-naphthyl), 7.51-7.40 (1H, m, CH-naphthyl), 5.93 (1H,d, H1′-guanosine), 4.62-4.57 (2H, m, H3′-guanosine, H4′-guanosine), 4.24(2H, m, H5′guanosine), 4.03-3.98 (3H, m, CHα, CH₂-ethyl), 1.31 (3H, d,CH₃-alanine, J=7.9 Hz), 1.15 (3H, m, CH₃-ethyl), 1.00 (3H, m,CH₃-2′-guanosine).

MS (ES) m/e: 625.3 (MNa⁺, 100%); Accurate mass: C₂₆H₃₁N₆O₉NaP required625.1795, found 6251788.

Anal. Calc. for C₂₆H₃₁N₆O₉P: C 51.83%, H 5.19%, N 13.95%. Found: C51.86%, H 5.10%, N 12.04%.

Example 8 Synthesis of 2′,3′-O,O-isopropylidyn-β-2′-methyl-guanosine5′-O-[phenyl(tert-butoxy-L-alaninyl)]phosphate

Prepared according to Standard Procedure C2, from2′,3′-O,O-isopropylidyn-β-2′-methyl-guanosine (120 mg, 0.355 mmol),^(t)BuMgCl (0.70 ml, 1M solution in THF, 0.711 mmol) andα-naphthyl(tert-butoxy-L-alaninyl)phosphorochloridate (0.70 ml ofsolution 1M in THF, 0.711 mmol). The crude was purified by columnchromatography, using as eluent CHCl₃/MeOH (95:5). The obtained pureproduct was a white solid (24 mg, 0.036 mmol, 10%).

δ_(P) (d₄-CH₃OH): 4.41, 4.32; δ_(H) (d₄-CH₃OH): 8.20 (1H, s,H8-guanosine), 7.89 (1H, m, CH-naphthyl), 7.73 (1H, m, CH-naphthyl),7.59-7.54 (4H, m, 4 CH-naphthyl), 7.49-7.42 (1H, m, CH-naphthyl), 6.07(1H, d, H1′-guanosine), 4.62-4.40 (4H, m, H3′-guanosine, H4′-guanosine,2H5′guanosine), 3.99-3.86 (1H, m, CHα), 1.58 (3H, d, CH₃-isoprpylidine,J=13.7 Hz), 1.44 (9H, s, 3 CH₃-tert-butyl), 1.38-1.34 (6H, m,CH₃-alanine, CH₃-isoprpylidine), 1.01 (3H, m, CH₃2′-guanosine).

Synthesis of β-2′-methyl-guanosine5′-O-[α-naphthyl(tert-butoxy-L-alaninyl)]phosphate (CHC8)

Prepared according to Standard Procedure C4, from2′,3′-O,O-isopropylidyn-β-2′-methyl-guanosine5′-O-[α-naphthyl(tert-butoxy-L-alaninyl)]phosphate (24 mg, 0.036 mmol),and 10 ml of a solution 60% of CH₃COOH in water. The crude was purifiedby column chromatography, using as eluent for the first CHCl₃/MeOH(85:5) followed by a semi-preparative HPLC. The obtained pure productwas a white solid (4 mg, 0.018 mmol, 17%).

δ_(P) (d₄-CH₃OH): 4.23, 4.10; δ_(H) (d₄-CH₃OH): 8.20 (1H, m,H8-guanosine), 7.85 (1H, m, CH-naphthyl), 7.67 (1H, m, CH-naphthyl),7.57 (4H, m, 4 CH-naphthyl), 7.53-7.43 (1H, m, CH-naphthyl), 6.00 (1H,d, H1′-guanosine), 4.61-4.55 (2H, m, H3′-guanosine, H4′-guanosine), 4.25(2H, m, 2H5′guanosine), 4.00-3.97 (1H, m, CHα), 1.47 (9H, s, 3CH₃-tert-butyl), 1.36 (3H, m, CH₃-alanine), 1.00 (3H, m,CH₃2′-guanosine).

Example 9 Synthesis of 2′,3′-O,O-isopropylidene-β-2′-methyl-guanosine5′-O-[phenyl(benzoxy-Lalaninyl)]phosphate

Prepared according to Standard Procedure C2, from2′,3′-O,O-isopropylidene-β-2′-methyl-guanosine (120 mg, 0.355 mmol),^(t)BuMgCl (1.0 ml, 1M solution in THF, 1.07 mmol) andphenyl(benzoxy-L-alaninyl)phosphorochloridate (1.0 ml of solution 1M inTHF, 1.07 mmol). The crude was purified by column chromatography, usingas eluent CHCl₃/MeOH (9:1) followed by semi-preparative HPLC. Theobtained pure product was a white solid (40 mg, 0.061 mmol, 17%).

δ_(P) (d₄-CH₃OH): 4.63, 4.37; δ_(H) (d₄-CH₃OH): 7.85 (1H, d,H8-guanosine, J=5.7 Hz), 7.36-7.34 (5H, m, 2 CH-phenyl, 3 CH-benzyl),7.33-7.26 (5H, m, 2 CH-benzyl, 3 CH-phenyl), 6.02 (1H, d, H1′-guanosine,J=11.4 Hz), 5.16 (2H, s, CH₂-benzyl), 4.67 (1H, d, H3′-guanosine, J=1.1Hz), 4.54-4.43 (1H, m, H4′-guanosine), 4.31 (2H, H5′guanosine), 4.10(1H, m, CHα), 1.61 (3H, s, CH₃-isopropylidine), 1.53 (3H, s,CH₃-isopropylidine), 1.39 (3H, d, CH₃-alanine, J=8.4 Hz), 1.00 (3H, s,CH₃-2′-guanosine).

Synthesis of β-2′-methyl-guanosine5′-O-[phenyl(benzoxy-L-alaninyl)]phosphate (CHC9)

Prepared according to Standard Procedure C4, from2′,3′-O,O-isopropylidene-β-2′-methyl-guanosine5′-O-[phenyl(benzoxy-L-alaninyl)]phosphate (40 mg, 0.061 mmol), and 10ml of a solution 60% of CH₃COOH in water at 90° C. for 15 hours. Thecrude was purified by column chromatography, using as eluent for thefirst CHCl₃/MeOH (85:5) followed by a semi-preparative HPLC. Theobtained pure product was a white solid (15 mg, 0.024 mmol, 40%).

δ_(P) (d₄-CH₃OH): 4.27, 4.10; δ_(H) (d₄-CH₃OH): 7.92 (1H, d,H8-guanosine, J=8.3 Hz), 7.37-7.29 (5H, m, 2 CH-phenyl, 3 CH-benzyl),7.25-7.18 (5H, m, 2 CH-benzyl, 3 CH-phenyl), 5.96 (1H, d, H1′-guanosine,J=2.3 Hz), 5.15 (2H, s, CH₂-benzyl), 4.43-4.35 (2H, m, H3′-guanosine,H4′-guanosine), 4.33-4.28 (1H, m, H5′-guanosine), 4.24-4.19 (1H, m,H5′-guanosine), 4.08-3.93 (1H, m, CHα), 1.35 (3H, m, CH₃-alanine), 1.24(3H, s, CH₃-2′-guanosine).

Example 10 Synthesis of 2′,3′-O,O-isopropylidene-β-2′-methyl-guanosine5′-O-[phenyl(methoxy-L-alaninyl)]phosphate

Prepared according to Standard Procedure C2, from2′,3′-O,O-isopropylidene-β-2′-methyl-guanosine (130 mg, 0.385 mmol),^(t)BuMgCl (0.96 ml, 1M solution in THF, 0.96 mmol) andα-naphthyl(methoxy-L-alaninyl)phosphorochloridate (0.96 ml of solution1M in THF, 0.96 mmol). The crude was purified by column chromatography,using as eluent CHCl₃/MeOH (97:3). The obtained pure product was a whitesolid (26 mg, 0.041 mmol, 11%).

δ_(P) (d₄-CH₃OH): 4.51, 4.45; δ_(H) (d₄-CH₃OH): 8.21 (1H, d,H8-guanosine, J=7.5 Hz), 7.91-7.89 (1H, m, CH-naphthyl), 7.73 (1H, m,CH-naphthyl), 7.58-7.53 (4H, m, 4 CH-naphthyl), 7.48-7.45 (1H, m,CH-naphthyl), 6.09 (1H, d, H1′-guanosine, J=7.4 Hz), 4.63 (1H, d,H3′-guanosine, J=3.0 Hz), 4.57-4.53 (2H, m, H4′-guanosine), 4.43-4.41(2H, m, H5′guanosine), 4.12-4.05 (1H, m, CHα), 3.62 (3H, d, CH₃-methyl,J=10.1 Hz), 1.59 (3H, d, CH₃-isopropylidine, J=7.9 Hz), 1.40 (3H, d,CH₃-alanine, J=3.4 Hz), 1.35 (3H, d, CH₃-isopropylidine, J=7.2 Hz), 1.05(3H, d, CH₃-2′-guanosine, J=7.0 Hz).

Synthesis of β-2′-methyl-guanosine5′-O-[α-naphthyl(methoxy-L-alaninyl)]phosphate (CHC10)

Prepared according to Standard Procedure C4, from2′,3′-O,O-isopropylidene-β-2′-methyl-guanosine5′-O-[α-naphthyl(methoxy-L-alaninyl)]phosphate (26 mg, 0.041 mmol), and10 ml of a solution 60% of CH₃COOH in water at 90° C. for 15 hours. Thecrude was purified by column chromatography, using as eluent for thefirst CHCl₃/MeOH (92:8). The obtained pure product was a white solid(4.1 mg, 0.007 mmol, 17%).

δ_(P) (d₄-CH₃OH): 4.35, 4.26; δ_(H) (d₄-CH₃OH): 8.20 (1H, d,H8-guanosine, J=5.8 Hz), 7.91-7.87 (2H, m, CH-naphthyl), 7.70 (1H, m,CH-naphthyl), 7.58-7.52 (3H, m, 3 CH-naphthyl), 7.50-7.41 (1H, m,CH-naphthyl), 5.93 (1H, s, H1′-guanosine), 4.58-4.56 (2H, m,H3′-guanosine, H4′-guanosine), 4.29-4.21 (2H, m, H5′guanosine),4.06-4.03 (1H, m, CHα), 3.56 (3H, d, CH₃-methyl, J=1.7 Hz), 1.31 (3H, d,CH₃-alanine, J=7.4 Hz), 1.00 (3H, d, CH₃-2′-guanosine, J=12.4 Hz).

Example 11 Synthesis of 2′,3′-O,O-isopropylidene-β-2′-methyl-guanosine5′-O-[phenyl(methoxy-L-alaninyl)]phosphate

Prepared according to Standard Procedure C2, from2′,3′-O,O-isopropylidene-β-2′-methyl-guanosine (140 mg, 0.415 mmol),^(t)BuMgCl (1.04 ml, 1M solution in THF, 1.04 mmol) andphenyl(methoxy-L-alaninyl)phosphorochloridate (1.04 ml of solution 1M inTHF, 1.04 mmol). The crude was purified by column chromatography, usingas eluent CHCl₃/MeOH (97:3). The obtained pure product was a white solid(21 mg, 0.036 mmol, 9%).

δ_(P) (d₄-CH₃OH): 4.09, 3.91; δ_(H) (d₄-CH₃OH): 7.88, 7.80 (1H, d,H8-guanosine), 7.41-7.35 (2H, m, CH-phenyl), 7.30-7.20 (3H, m, 3CH-phenyl), 6.14 (1H, d, H1′-guanosine, J=11.8 Hz), 4.69 (1H, d,H3′-guanosine, J=2.9 Hz), 4.49-4.39 (3H, m, H4′-guanosine,H5′guanosine), 4.04-3.99 (1H, m, CHα), 3.70 (3H, d, CH₃-methyl, J=12.7Hz), 1.63 (3H, d, CH₃-isopropylidine, J=2.3 Hz), 1.44 (3H, d,CH₃-alanine, J=3.1 Hz), 1.41 (3H, d, CH₃-isopropylidine, J=6.8 Hz), 1.10(3H, d, CH₃-2′-guanosine, J=6.5 Hz).

Synthesis of β-2′-methyl-guanosine5′-O-[phenyl(methoxy-L-alaninyl)]phosphate (CHC11)

Prepared according to Standard Procedure C4, from2′,3′-O,O-isopropylidene-β-2′-methyl-guanosine5′-O-[phenyl(methoxy-L-alaninyl)]phosphate (21 mg, 0.036 mmol), and 10ml of a solution 60% of CH₃COOH in water at 90° C. for 15 hours. Thecrude was purified by column chromatography, using as eluent for thefirst CHCl₃/MeOH (92:8). The obtained pure product was a white solid(7.0 mg, 0.013 mmol, 36%).

δ_(P) (d₄-CH₃OH): 4.15, 3.90; δ_(H) (d₄-CH₃OH): 8.96 (1H, br,H8-guanosine), 7.40-7.35 (2H, m, CH-phenyl), 7.29-7.20 (3H, m, 3CH-phenyl), 6.08 (1H, d, H1′-guanosine, J=8.5 Hz), 4.55-4.49 (2H, m,H3′-guanosine, H4′-guanosine), 4.26 (1H, m, H5′guanosine), 4.17-4.11(1H, m, H5′-guanosine), 4.00-3.97 (1H, m, CHα), 3.73 (3H, d, CH₃-methyl,J=11.1 Hz), 1.36 (3H, d, CH₃-alanine, J=7.1 Hz), 1.41 (3H, d,CH₃-isopropylidine, J=6.8 Hz), 1.14 (3H, d, CH₃-2′-guanosine, J=4.9 Hz).

Each of compounds CHC1 to CHC9, as prepared according to Examples 1 to11, respectively, was tested for its potency with respect to HCV.

The anti-HCV assays employed were:

Anti-HCV assay in Huh 7 cells. Huh 7 cells containing subgenomic HCVreplicons I₃₈₉luc-ubi-neo/NS3-3′/5.1 (Huh 5-2) or I₃₇₇/NS3-3′/wt (Huh9-13) have been described (Lohmann V, Korner F, Koch J, Herian U,Theilmann L, Bartenschlager R. (1999) Replication of subgenomichepatitis C virus RNAs in a hepatoma cell line. Science 285:110-113.Lohmann V, Korner F, Dobierzewska A, Bartenschlager R. (2001) Mutationsin hepatitis C virus RNAs conferring cell culture adaptation. J Virol.75:1437-1449.). Cells were grown in Dulbecco's modified Eagle's Medium(DMEM; Gibco, Merelbeke, Belgium) supplemented with 10% heat-inactivatedfetal bovine serum (FCS) (Integro, Zaandam, The Netherlands), 1×non-essential amino acids (Gibco), 100 IU/ml penicillin (Gibco), 100μg/ml streptomycin (Gibco) and 250 μg/ml Geneticin (G418, Gibco) for Huh5-2 cells, 1000 μg/ml G418 for Huh 9-13 cells

Anti-HCV Assay in Huh 5-2 Cells.

Huh 5-2 cells were seeded at a density of 5×10³ per well in a tissueculture treated white 96-well view plate (Packard, Canberra, Canada) incomplete DMEM supplemented with 250 μg/ml G418. Following incubation for24 h at 37° C. (5% CO₂) medium was removed and serial dilutions incomplete DMEM (without G418) of the test compounds were added in a totalvolume of 100 μl. After 4 days of incubation at 37° C., cell culturemedium was removed and luciferase activity was determined using theSteady-Glo luciferase assay system (Promega, Leiden, The Netherlands);the luciferase signal was measured using a Luminoskan Ascent (Thermo,Vantaa, Finland). The 50% effective concentration (EC₅₀) was defined asthe concentration of compound that reduced the luciferase signal by 50%.

Anti-HCV Assay in Huh 9-13 Cells.

Huh 9-13 cells were seeded at a density of 5×10³ cells per well in96-well cell culture plates in complete DMEM supplemented with 1000μg/ml G418. Following incubation for 24 h at 37° C. cell culture mediumwas removed and serial dilutions of the test compounds in complete DMEMwithout G418 were added in a total volume of 100 μl. After 4 days ofincubation at 37° C., cell culture fluid was removed and monolayers werewashed once with phosphate-buffered saline. Cells were lysed in 350 μlRLT buffer (Qiagen, Venlo, The Netherlands) according to theManufacturer's instruction. Lysates were stored at −80° C. until furtheruse.

RT-qPCR.

A 25 μL RT-qPCR reaction contained 12.5 μl 2× reaction buffer(Eurogentec, Seraing, Belgium), 6.3 μl H₂O, 5 μl total cellular RNAextract and in the case of Huh 9-13 and HuH6 samples 300 nmol/Lneo-forward primer [5′-CCG GCT ACC TGC CCA TTC-3′], 300 nmol/Lneo-reverse primer [5′-CCA GAT CAT CCT GAT CGA CAA G-3′], 300 nmol/Lneo-probe [5′-FAM-ACA TCG CAT CGA GCG AGC ACG TAC-TAMRA-3′] or forHuh-mono samples 300 nmol/L UTR-forward primer [5′-ACG CAG AAA GCG TCTAGC CAT GGC GTT AGT-3′], 300 nmol/L UTR-reverse primer [5′-TCC CGG GGCACT CGC AAG CAC CCT ATC AGG-3′], 300 nmol/L UTR-probe [5′-FAM-TGG TCTGCG GAA CCG GTG AGT ACA CC-TAMRA-3′]. The RT step was performed at 48°C. for 30 minutes, 15 minutes at 95° C. and subsequent PCR amplificationof 40 cycles of denaturation at 94° C. for 20 seconds and annealing andextension at 60° C. for 1 minute in an ABI 7000 sequence detector. The50% effective concentration (EC₅₀) was defined as the concentration ofcompound that reduced replicon RNA content by 50%.

The results in terms of HCV EC₅₀/μM and CC₅₀/μM are given in Table Ibelow.

In Table I:

A refers to 9-linked adenine, G refers to 9-linked guanine, Nap refersto 1-naphthyl (—C₁₀H₉), Ph refers to phenyl (—C₆H₅), Et refers to ethyl(CH₃CH₂—), Bn refers to benzyl (C₆H₅CH₂—), t-Bu refers to tertiary butyl((CH₃)₃C—) and Me refers to methyl (CH₃—).

TABLE I HCV HCV Huh 5-2 Huh 9-13 Compound Base Ar R₃ EC₅₀/μM EC₅₀/μMCC₅₀/μM CHC1 A — — 0.14 29 0.08 >33 0.13 >33 CHC2 A Nap Et 0.12 >50 CHC3A Nap Bn 0.16 44 CHC4 A Nap t-Bu 2.36 >50 CHC5 G — — 3 1.5 >50 5 >50CHC6 G Nap Bn 0.08 0.06 >50 0.032 >50 0.11 >50 0.13 >50 0.044 >50 CHC7 GNap Et 0.15 >50 0.2 >50 0.16 >50 CHC8 G Nap t-Bu >50 >50 CHC9 G Ph Bn 364.1 >50 CHC10 G Ph Me 0.87 >50 0.88 >50 CHC11 G Nap Me 0.14 >50 0.063>50

The data in Table I show that each of the compounds CHC6 and CHC7embodying the present invention exhibits greater potency with respect toHCV than compound CHC5 which corresponds to the free nucleoside 9-linkedguanine.

A comparison of the data in Table I with respect to each of compoundsCHC6 and CHC9, and with respect to each of compounds CHC10 and CHC11,shows that the enhanced potency with respect to HCV is attributable tothe presence in compounds CHC6 and CHC11, respectively, of Ar being1-naphthyl.

Table II below sets out the structures of the presently exemplifiedcompounds CHC1 to CHC11 in terms of formula I above, with in each caseZ═H and Q=O.

TABLE II Compound X Y T″ V T Ar R₁ R₂ R₃ R₄ CHC1 NH₂ H H OH H — — — — —CHC2 NH₂ H H OH H C₁₀H₇ CH₃ H CH₃CH₂ H CHC3 NH₂ H H OH H C₁₀H₇ CH₃ HC₆H₅CH₂ H CHC4 NH₂ H H OH H C₁₀H₇ CH₃ H t-C₄H₉ H CHC5 ═O NH₂ H OH H — —— — — CHC6 ═O NH₂ H OH H C₁₀H₇ CH₃ H C₆H₅CH₂ H CHC7 ═O NH₂ H OH H C₁₀H₇CH₃ H CH₃CH₂ H CHC8 ═O NH₂ H OH H C₁₀H₇ CH₃ H t-C₄H₉ H CHC9 ═O NH₂ H OHH C₆H₅ CH₃ H C₆H₅CH₂ H CHC10 ═O NH₂ H OH H C₆H₅ CH₃ H CH₃ H CHC11 ═O NH₂H OH H C₁₀H₇ CH₃ H CH₃ H

Where Ar is C₁₀H₇, it is 1-naphthyl. Where X is NH₂, n is 0. Where X is═O, n is 1.

Each of compounds CHC1, CHC5, CHC9 and CHC10 is a comparative compound.

Compound CHC1 corresponds to the non-phosphoramidated, free nucleoside9-linked adenine.

Compound CHC5 corresponds to the non-phosphoramidated, free nucleoside9-linked guanine.

The invention claimed is:
 1. A compound of formula I:

wherein: Ar is naphthyl; T is selected from the group consisting ofhydrogen (H—), fluoro (F—), methyl (—CH₃) and ethyl (—C₂H₅); V isselected from the group consisting of hydrogen (—H), fluoro (—F) and OT′where T′ is selected from the group consisting of hydrogen (—H), andmethyl (—CH₃); T″ is hydrogen (—H); n is 0 or 1, wherein when n is 1, Xis ═O, and when n is 0, a double bond exists between position 3 andposition 4 and X is selected from the group consisting of H, OH, F, CI,Br, I, C₁₋₆alkyl and NR₅R₆, where each of R₅, and R₆ is independentlyselected from H and C₁₋₆ alkyl; Z is selected from the group consistingof H, F, and Cl; Y is selected from the group consisting of H, F, Cl,Br, NH₂ and NR₅R₆, where each of R₅ and R₆ is independently selectedfrom H and C₁₋₆-alkyl; Q is selected from the group consisting of O, andS; each of R₁ and R₂ is independently selected from the group consistingof H, C₁₋₂₀alkyl, C₂₋₂₀alkenyl, C₁₋₂₀alkoxy, C₁₋₂₀alkoxyC₁₋₂₀alkyl,C₁₋₂₀alkoxyC₆₋₃₀aryl, C₂₋₂₀alkynyl, C₃₋₂₀cycloalkylC₆₋₃₀aryl,C₆₋₃₀aryloxy and C₅₋₂₀heterocyclyl, any of which is optionallysubstituted with a substituent selected from the group consisting ofelectron donating and electron withdrawing moieties; each of R₃ and R₄is independently selected from the group consisting of H, C₁₋₂₀alkyl,C₂₋₂₀alkenyl, C₁₋₂₀alkoxy, C₁₋₂₀alkoxyC₁₋₂₀alkyl, C₁₋₂₀alkoxyC₆₋₃₀aryl,C₂₋₂₀alkynyl, C₃₋₂₀cycloalkylC₆₋₃₀aryl, C₆₋₃₀aryloxy andC₅₋₂₀heterocyclyl, any of which is optionally substituted with asubstituent selected from the group consisting of electron donating andelectron withdrawing moieties; with the proviso that —R₁ and R₄ aretogether defined as a —(CH₂)₃— alkylene chain; and pharmaceuticallyacceptable salts thereof.
 2. A compound according to claim 1 wherein Aris unsubstituted 1-naphthyl.
 3. A compound according to claim 1 whereinT is H, V is OH and T″ is H.
 4. A compound according to claim 1 whereinn is 1, X is ═O and Y is NH₂.
 5. A compound according to claim 4 whereinZ is H.
 6. A compound according to claim 1 wherein n is 0, a double bondexists between position 3 and position 4, X is selected from the groupconsisting of NH₂, F, Cl and NR₅R₆ where one of R₅ and R₆ is H and theother of R₅ and R₆ is C₁₋₆-alkyl.
 7. A compound according to claim 6where X is NH₂, Y is H and Z is H.
 8. A compound according to claim 1wherein Q is O.
 9. A compound according to claim 1 wherein R₃ is alkyl.10. A compound according to claim 1 wherein R₃ is selected from thegroup consisting of methyl, ethyl, 2-propyl, n-propyl, cyclohexyl,2-butyl and benzyl.
 11. A compound according to claim 1 wherein R₄ is H.12. A compound according to claim 1 wherein R₁ and R₂ are selected suchthat the moiety —N—CR₁R₂—COO— corresponds to the structure of a naturalamino acid incorporated into the generic structure of formula I.
 13. Acompound according to claim 1 wherein each of R₁ and R₂ is independentlyselected from methyl (—CH₃) and H.
 14. A compound according to claim 13wherein one of R₁ and R₂ is methyl and one of R₁ and R₂ is H such thatthe C atom bearing R₁ and R₂ has chirality L as in natural alanine. 15.A compound according to claim 1 wherein Ar is unsubstituted.
 16. Acompound according to claim 1 comprising the diastereoisomer R_(P), thediastereoisomer S_(P) or a mixture of the diastereoisomers R_(P) andS_(P).
 17. A compound selected from the group comprising:β-2′-methyl-adenosine 5′-O-[α-naphthyl(ethoxy-L-alaninyl)]phosphate;β-2′-methyl-adenosine 5′-O-[α-naphthyl(benzoxy-L-alaninyl)]phosphate;β-2′-methyl-adenosine5′-O-[α-naphthyl(tert-butoxy-L-alaninyl)]phosphate;β-2′-methyl-guanosine 5′-O-[α-naphthyl(benzoxy-L-alaninyl)]phosphate;β-2′-methyl-guanosine 5′-O-[α-naphthyl(ethoxy-L-alaninyl)]phosphate;β-2′-methyl-guanosine5′-O-[α-naphthyl(tert-butoxy-L-alaninyl)]phosphate; andβ-2′-methyl-guanosine 5′-O-[α-naphthyl(methoxy-L-alaninyl)]phosphate.18. A pharmaceutical composition comprising a compound according toclaim 1 in combination with a pharmaceutically acceptable carrier,diluent or excipient.
 19. A method of treatment of a viral infection,comprising administering to a patient in need an effective dose of thecompound according to claim
 1. 20. The method according to claim 19wherein the viral infection is hepatitis C virus.
 21. A method ofpreparing a pharmaceutical composition comprising the step of physicallymixing a compound according to claim 1 with a pharmaceuticallyacceptable excipient, carrier or diluent.
 22. A process for thepreparation of a compound of formula I as defined in claim 1, theprocess comprising reacting a compound of formula III:

with a compound of formula IV:

where Ar, T, V, T″, n, X, Y, Z, Q, R₁, R₂, R₃ and R₄, have the meaningsas defined in claim 1.